This invention relates to a precompression pump, particularly for the atomized dispensing of products in liquid or similar form from a container, of the type comprising a body, an at least partly hollow stem mobile within said body against the action of a return spring, a piston mounted mobile on the stem against the action of elastic means so as to open a passage towards the cavity in the stem, the piston defining with the body a suction and metering chamber, and an intake valve means for the access of said liquid to said chamber.
Precompression pumps are pumps of the type which allow the product to be dispensed only when a pressure lying between predetermined limits acts on it. Precompression pumps of the indicated type are known for example from U.S. Pat. Nos. 3,463,093 (see FIG. 2) and 4,113,145 (see FIG. 27).
In known pumps of this type, the return spring is situated in the suction and metering chamber, so that it is in contact with the liquid to be dispensed. Because of this, the spring even if made of stainless steel can contaminate the product by transferring to it any substances, such as lubricants, which were used during the operations involved in its manufacture, such as the extrusion of the wire from which the spring is formed and the subsequent winding of the spring, and have remained on it. This is unacceptable when the product to be dispensed is a pharmaceutical or cosmetics product. In addition, the spring located in the suction and metering chamber considerably increases the clearance volume of the pump.